Honeycomb materials are lightweight and well known for providing elevated stiffness, strength, and mechanical energy absorption properties. When subjected to in-plane compression, honeycomb structures typically undergo an initial region of elastic deformation, in which the cell walls bend, compress, and/or extend elastically. The stiffness depends on the cell structure. The region of elastic deformation typically ends when the mesostructure reaches a plateau stress, at which point the individual cell walls begin to collapse by buckling. At extremely low relative densities, elastic buckling can occur, but for most practical relative densities, collapse is associated with plastic buckling and yielding. With increasing loads, the mesostructure continues to absorb energy as cell walls progressively collapse. Eventually, when cell wall collapse is complete, the mesostructure densifies, and stiffness rapidly approaches that of the constituent material in the cell walls.
However, known honeycomb structures exhibit various shortcomings. For example, as a typical honeycomb structure is compressed, it elastically deforms until the cell walls begin to collapse. Once the cell walls collapsed, they cannot recover their original form. As a result, a typical honeycomb structure that experiences a force sufficient to collapse cell walls will never be able to recover its original form. While this type of honeycomb structure may still provide impact absorbance initially, it would not be able to provide the same level of impact absorbance afterwards. In other words, the energy absorption of a typical honeycomb structure is not recoverable.
A typical honeycomb structure therefore has a distinct disadvantage when used for energy absorption in an apparatus that is expected to experience more than one application of external force. Instead, the typical honeycomb structure must be repaired or replaced whenever it is subjected to a force sufficient to cause collapse. This can increase cost, lower efficiency, and increase the maintenance requirements for particular structures incorporating typical honeycomb designs. There is a distinct need for a honeycomb structure that provides high levels of recoverable energy absorption.
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